The present invention relates generally to the field of cellulosic pulp processing, and more specifically to building products such as particle board, wall board, pressed wood, oriented strand board (OSB), bound with nanocellulose fibers as the adhesive.
Capturing carbon from the air is a difficult and expensive task. A recent review article (See, Spigarelli B. P., and S. K. Kawatra, “Opportunities and challenges in carbon dioxide capture”, J. of CO2 Utilization 1: 69-87 (2013) documents the various approaches. The cost to simply remove CO2 from stack gas is quite significant. For example, CO2 can be scrubbed from stack gasses at low cost and precipitated with calcium to form calcium carbonate. However, the lime that is needed for this process is produced by burning calcium carbonate that results in the release of CO2, there is no net reduction of CO2 and in fact, the net result is a release of carbon from the fuel used to burn the limestone. Membrane processes require large capital investments and energy costs. Therefore, any product that is produced from CO2 captured from a stack gas has the cost burden of capture on top of other process costs to convert it into a product.
Of course, plants sequester carbon as they grow. However, after a plant/tree dies, it will be burned or decompose, releasing the CO2. Using plant material to produce biofuels is one method to reduce our use of petroleum, but CO2 is released upon burning of these fuels. Only when we convert the carbon in the plant material into products that last a long time will a net reduction of CO2 be realized.
The present invention seeks to reduce the release of CO2 into the atmosphere by using the carbon found in plant material to produce useful building materials that will last several decades. Doing so utilizes carbon that is already sequestered by plants, and incorporates that carbon into novel and valuable products that will last for many years. Large quantities of carbon can be captured for many years into the future if even only some of the building products described herein are commercialized.
In the western US and Canada, there is a large infestation of pine beetle that has killed millions of square miles of lodge pole and other pines. As of 2006, the beetle had killed over 130,000 km2 and is thought to be the largest insect tree kill in recorded history. The carbon that is sequestered in this wood may be in the order of 10,000 mtons. In addition, in the western US, thinning and clearing of forests are needed for fire prevention. However, there is no commercial use of this wood that can support the cost of thinning operations. If forest fires break out or as the natural decomposition of the wood occurs, this carbon will be released as CO2. Dead trees are only good for saw timber for a few years. Its value then decreases rapidly. Once a tree falls, it will decompose and release the carbon. If this wood is converted into fuel or burned to generate heat or electricity, or involved in a forest fire, this carbon ends up in the atmosphere. It would be advantageous to avoid this result.
An additional but distinct environmental problem is the release of formaldehyde into living spaces. Conventional composite wood products such as particle board typically contain a formaldehyde-based binder system, which releases the dangerous formaldehyde into a living space. The release of formaldehyde into a living space causes respiratory disorders, neurological disorders, cancer, and reproductive issues.
According to the Formaldehyde Emissions Standards for Composite Wood Products; Proposed Rule [RIN 2070-AJ92; FRL-9342-3], the benefits of avoiding formaldehyde are substantial. “For the subset of health effects where the results were quantified, the estimated annualized benefits (due to avoided incidence of eye irritation and nasopharyngeal cancer) are $20 million to $48 million per year using a 3% discount rate, and $9 million to $23 million per year using a 7% discount rate. There are additional unquantified benefits due to respiratory and other avoided health effects.” The “Alternative Resin Binders for Particleboard, Medium Density Fiberboard (MDF), and Wheatboard” report issued by the Global Health and Safety Initiative, indicates that no alternatives have been identified that are 100% safe. “At this point in the development of alternatives to urea formaldehyde (UF) resins in particleboard, MDF, and wheatboard products, there has yet to be a product that can replace UF that does not raise some environmental health concerns.”
Nanofibrillated cellulose have been shown to be useful as reinforcing materials in wood and polymeric composites, as barrier coatings for paper, paperboard and other substrates, and as a paper making additive to control porosity and bond dependent properties. For example, a review article by Siro I., and D. Plackett, “Microfibrillated cellulose and new nanocomposite materials: a review”, Cellulose 17:459-494 (2010) discusses recent trends. FIG. 1 from Siro et al (reproduced as FIG. 1 herein) illustrates the explosion of publications in this area recently. A number of groups are looking at the incorporation of nanocellulose materials into paper or other products, but commercial demonstration related to the use of this material has yet to be documented. Other research groups are looking at using this material at low concentrations as reinforcements in plastic composites. In these cases, the prevalent thinking is that nanofibers can be used in combination with the polymeric binder in composites, typically as reinforcement, not as a replacement adhesive in lieu of the polymers. For example, Veigel S., J. Rathke, M. Weigl, W. Gindl-Altmutter, in “Particle board and oriented strand board prepared with nanocellulose-reinforced adhesive”, J. of Nanomaterials, 2012, Article ID 158503 1-8, (2012) discuss using nanocellulose to reinforce the polymeric resins, but still retain resins in the system. Many of the other ideas by other groups are only using small volumes of fibers in high value products.
It would be advantageous if there could be developed improved processes for sequestration of carbon to prevent the release of CO2 into the atmosphere. It would also be advantageous if building products could be developed utilizing cellulose nanofibers that otherwise would be wasted or would release CO2 into the atmosphere if used in conventional ways. It would be especially advantageous if building products having superior properties could be developed in the process.